Pressure responsive flow control valve for directional control valve



1965 H. H. SCHMIEL ETAL 3,213,374

PRESSURE RESPONSIVE mow coumnor, mvm FOR DIRECTIONAL CQNTROLI VALVEFiled June 2, 1961 FIG 2 8 v 5 38 FIG 5 FIG 4 s7 H; FIG 6 62 64 6|INVENTORS nw' M HERBERT d. SCHMIEL a 5 ROBERT B. OLEN ATTORNEYS UnitedStates Patent 3,213,874 PRESSURE RESPONSIVE FLOW CONTRDL VALVE FORDIRECTIONAL CQNTROL VALVE Herbert H. Schmiel, Willoughby, and Robert B.Olen,

Salem, Ohio, assignors to Parker-Hannifin Corporation,

Cleveland, Ohio, a corporation of Ohio Filed June 2, 1961, Ser. No.114,361 4 Claims. (Cl. 137-99) The present invention relates generallyas indicated to a pressure responsive flow control valve for adirectional control valve and more particularly to a fluid power systemhaving a fluid motor and a pilot operated control which is effective tolock the movable component of the motor against movement and to regulatethe flow of fluid during the movement of said component.

In the case of directional control valves for hydraulic power cylindersit is conventional practice simply to provide conduits interconnectingthe ports of the directional control valve and the actuating cylinderand to provide metering slots in said valve which, by gradual actuationof said valve, results in smooth acceleration and deceleration of thepiston in said cylinder. However, operators \of front end loaders, powershovels, cranes, etc. are prone to shift the directional control valvesdirectly to selected operating positions with consequent shocks on thescoops, buckets, booms, etc. that are actuated by the associated powercylinders. Moreover, in systems wherein negative loads are imposed onthe power cylinders e.g. power lowering of booms having loaded buckets,it is desirable to limit the speed of movement of the piston so as toavoid severe shock when the movement of the load is arrested by shiftingthe directional control valve to off or neutral position, or by the loadengaging a positive stop position, or by the piston reaching the end ofits stroke.

Furthermore, spool-type directional control valves are in prevalent useand since the spools thereof are axial sliding fits in cylindrical boresof the valve housing, they are not fluid-tight and, therefore, when thespool is in neutral or off position, the piston in the power cylindermay gradually creep under the influence of a load thereon due to leakageof the fluid between the spool and its bore.

Accordingly, it is a principal object of this invention to provide, in afluid circuit between a spool valve and a power cylinder, a fluid-tightvalve assembly which will prevent displacement of fluid from thecylinder thereby to lock the piston therein. In the case of a doubleacting spool and double acting power cylinder, duplicate valveassemblies may be provided to prevent displacement of fluid from bothends of the cylinder, and consequently, the piston therein will bepositively locked against movement in either direction when the doubleacting directional control valve is in off or neutral position.

It is another object of this invention to provide a fluid pressureresponsive valve for a directional control valve of the characterindicated which has an associated dashpot effective to meter the fluidto or from the power cylinder for desired rate of acceleration of theactuation thereof, despite the fact that the directional control valvemay have been shifted to full flow position.

It is another object of this invention to provide a fluid power systemin which a flow control valve interposed between the directional controlvalve and the power cylinder is effective to limit the speed ofactuation of the latter as when the load on the cylinder is negative andof great magnitude.

Other objects and advantages of the present invention will becomeapparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of a fewof the various Ways in which the principle of the invention may beemployed.

In said annexed drawings:

FIG. '1 is a front elevation view of one embodiment of this invention;

FIG. 2 is a side elevation view as viewed from the right of FIG. 1;

FIG. 3 is a cross-section view taken substantially along line 33, FIG.2;

FIG. 4 is a fragmentary cross-section taken substantially along line4-4, FIG. 1;

FIGS. 5 and 6 are side elevation views of two forms of flow controlvalve elements;

FIG. 7 is a cross-section view of another embodiment of this invention;and

FIG. 8 is an enlarged fragmentary cross-section view of the lower valveassembly of FIG. 4.

Referring now more particularly to the drawings, and first to the formof the invention illustrated in FIGS. 1 to 6, the directional controlvalve 1 for the double acting power cylinder 2 comprises a housing 3having a pressure inlet port 4 which communicates with the tank returnport 5 by way of a bypass passage 6 intersecting the bore 7 in which thedouble acting spool 8 is axially slidable, the spool 8 having connectedat one end thereof a spring return mechanism 9 which automaticallyrestores the spool to neutral or off position (see FIG. 3) from eitherof its operating positions when axial force on the spool 8 is released.A relief valve 13 in housing 3 limits the pressure in the inlet chamber10, excess pressure being relieved to the tank port 5 via return passage11.

The inlet chamber 10 leads to a pair of feed passages 12; 12intersecting the spool bore 7, and straddling the feed passages 12; 12are the services ports 14; 14 which, as shown in FIG. 1, are adapted tobe connected to the ports at the ends of the power cylinder 2.

The spool 8 herein shown by way of example is of the double acting typehaving alternate lands and grooves arranged so that, upon axial movementof the spool 8 from the neutral position shown in FIG. 3, fluid underpressure passes from one feed passage 12 into the adjacent service port14 to actuate the piston 15 in the cylinder 2 in one direction and thefluid displaced from the other end of the cylinder 2 flows throughreturn port 5 to a fluid reservoir 16 via the other service port 14 andthe adjoining return passage 11.

The directional control valve structure thus far described is more orless conventional and well-known in the art. When the spool 8 isreturned from one operating position to neutral by spring mechanism 9,the fluid delivered by the system pump 17 to the inlet port 4 freelypasses through the housing 3 to the return port 5 via the aforesaidbypass passage 6 and usually the spool 8 will have lands blocking theservice ports 14. However, spool valves cannot be made fluid-tightexcept at great expense either by extremity fine machining or byemploying rubber-like sealing rings.

In the present case, in view of the provision of the pressure responsiveflow control and piston locking valve assembly 18 it is not required inthe neutral position to try to completely close off communicationbetween the service ports 14 and the return passages 11 and thus thespool 8 herein is formed with land portions 19 of substantially smallerdiameter than the spool bore 7.

The pressure responsive flow control 18 is embodied in the same housing3 as the spool 8. For a double acting spool 8, it is preferred to employduplicate valve assemblies disposed in the respective service ports 14.As best shown in FIG. 4, one valve assembly comprises a valve member 21held by spring 23 in position closing the lower service passage 14. Theother valve assembly 24 associated with the upper service port 14comprises a tubular valve body 25 held in place by a plug 26 threadedinto the housing 3 and having a seat against which the valve member 27is pressed by the spring 28.

The valve members 21 and 27 are, as shown, in coaxial alignment andbetween them is a pressure actuated plunger 30 which is slidablyreceived in a cylinder 30' interconnecting the upper and lower serviceports 14, 14. The plunger 30 has a cylindrical extension 30" on each endthereof, the upper extension being adapted to cooperate with a bushing39 disposed in the cylinder 30' to form a dashpot 31 as the plungermoves up, and the lower extension being adapted to cooperate with thewalls of the adjacent service port 14 to form a dashpot 32 when theplunger moves down. The plunger 30 also has opposite coaxial extensions34 and 35 adapted to engage the respective valve members 21 and 27 tounseat them. The ends of said extensions 34 and 35 are preferably ofabout the same diameters as the bores into which they extend, except fortapering flats 36 on opposite sides as clearly shown in FIG. 5, whereby,as will be seen hereafter, these heads or ends of extensions 34 and 35serve as metering or flow control means, depending on the extent ofmovement of the plunger 30.

If desired, the metering heads of the plunger extensions 35 may befrusto-conical, as shown at 37 in FIG. 6.

Insofar as operation is concerned, assuming that the spool 8 is inneutral position (FIG. 3), the spring-seated valve members 21 and 27will preclude displacement of fluid from either end of the powercylinder 2, whereby a load on the piston 15 in either direction will notcause movement thereof from its thus locked position. Now, supposing thespool 8 is moved downwardly from its FIG. 3 neutral position, it can beseen that fluid under pressure will flow from the upper feed passage 12into the upper service port 14 and as the pressure builds up in theservice passage 14, it acts downwardly on the area of the plunger 30 toforce the lower valve member 21 away from its seat, whereas the uppervalve member 27 will act as a check valve to permit flow of fluid fromthe upper service port 14 into the head end of the cylinder 2. Thepiston 15 therefore moves toward the right and the fluid displaced fromthe rod end of the cylinder 2 passes through the lower service port 14,through the open valve member 21 into the lower service port 14 andthence into the return passage 11. The dashpot 32 permits onlycontrolled slow movement of plunger 30 whereby the return fluid ismetered past the tapered sides 36 or 37 of the extension 34 until theneck of extension 34 is in bore portion 38. The inlet fluid is alsometered past the tapered sides 36 or 37 of the extension 35 until thehead reaches the enlarged bore portion of the bushing 39 in body 25. 7

Should the load on the piston 15 change from positive to negative withconsequent drop in the pressure acting on the upper side of the plunger30, and with an increase in the pressure in the return circuit acting onthe lower side of the plunger 34), the plunger 30 may move upward todecrease the inlet and return flow past the upper and lower meteringheads. Therefore, the piston 15 will be precluded from moving too fastunder the influence of such negative load.

Of course, when the double acting spool 8 is shifted upwardly from theFIG. 3 neutral position, the piston 15 in the cylinder 2 will be causedto move toward the left with incoming fluid flowing past the lower valvemember 21 which is then functioning as a check valve and the returningfluid flows past the upper valve member 27, which is now moved away fromits seat by the upward movement of the plunger 30 with its extension 35engaging and moving the upper valve member 27 away from its seat. Thedashpot 31 and the metering heads of extensions 34 and 35 are effectiveto meter inlet and return flow in the same way as explained above.

In FIG. 7 is shown an embodiment of the invention employing a pilotoperated lock flow control 40 which is separate of the double actingspool valve 41. Since, in this embodiment, for example, the tilt controlof a boom of a front end loader, or the like, has only a downward load42 on the piston there is no need for duplicate fluid pressureresponsive flow controls as in the case of FIGS. 1 to 6.

In this case, the directional control valve 41 has one service port 43connected to the upper rod end of the power cylinder 45 with a branch 46lea-ding to one side of a plunger 47 reciprocable in the body 48 of thepilot operated flow control valve 40. The other service port 49 of thedirectional control valve 41 is connected to the head end of thecylinder 45 via a passage 50 through the body 48. The aforesaid passage50 is formed with a seat 51 engaged by the valve member 52 biased byspring 53. In this case, the plunger 47 has an extension 54 whichprojects into the passage 56, there being a slight clearance between theextension 54 and the walls of the passage 56 to define a dashpot 57.Head 58 of extension 59 has V-shaped metering slots as shown to controlflow according to the axial position of the metering head 58 in bore 55.The end of the metering head 58 is adapted to engage the valve member 52to force it away from its seat 51.

Assuming now that it is desired to raise the piston 60 in the cylinder45 to raise the load 42, or to tilt the aforesaid boom upwardly, thedirectional control valve spool 61 will be shifted to communicate theleft service port 49 with the inlet 62 and thus the pressure will unseatthe valve member 52 so that fluid may flow into the head end of thecylinder 45. The fluid displaced from the rod end of the cylinder 45passes through the conduit 63 into the right service port 43 which thenis in communication with the return port 64.

Now, if it is desired to lower the piston 60 and thus the load 42thereon, the directional control valve 41 is actuated to communicate theinlet port 62 with the right service port 43 in which case fluid underpressure is delivered into the rod end of the cylinder 45 and the fluiddisplaced from the cylinder 45 will pass through the valve member 52which is gradually opened by the slowly moving plunger 47 to the leftservice port 49 which is in communication with the return port 64. Ifthe descent of the piston 60 and load 42 is more rapid than desired, thepressure acting on the end of the plunger 47 may decrease to the extentthat the pressure drop across valve member 52 is suflicient to move thelatter and also plunger 47 toward the right whereby the metering head 58in bore effects throttling of the return flow and consequent decrease inthe speed of descent of the piston 60. The dashpot 57, including dashpot65, assures desired slow and gradual movements of plunger 47 in oppositedirections to avoid shocks in the system.

In addition to, or in lieu of, the dashpots 31 and 32 aforesaid, thespring chambers behind the valve members 21 and 27 may constitutedashpots when said members are slide fits in their respective bores, asperhaps best seen in FIG. 8. Thus, the plunger 30 can only move at aslow rate to provide the desired meter-ing action.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

We therefore particularly point out and distinctly claim as ourinvention:

1. A flow control valve comprising a body having a pair of passages;valve members in the respective passages; springs biasing said valvemembers to positions closing the respective passages; said body having acylinder therein in fluid communication with said passages upstream ofsaid valve members; a plunger in said cylinder having one end exposed tofluid under pressure in one of said passages and the other end exposedto fluid under pressure in the other of said passages; said plungerbeing adapted to be moved by predominant fluid pressure in eitherpassage into engagement with the valve member in the other passage tomove it to a position opening said other passage; said plunger havingflow metering means on either end thereof which are operativesimultaneously to meter the flow through both of said passages when oneof said passages is opened by engagement of said plunger with itsrespective valve member, and the other of said passages is opened byfluid pressure exerted on its respective valve member.

2. The flow control valve of claim 1 wherein said plunger end portionsare tapered.

3. The flow control valve of claim 1 wherein said plunger end portionshave tapered sides to define segmental flow passages.

4. The flow control valve of claim 1 wherein said plunger end portionsare of frusto-conical form.

References Cited by the Examiner UNITED STATES PATENTS 1,176,972 3/16Menzies 251-52 1,531,146 3/25 Skortz 251-52 2,117,182 5/38 Lewis137-6253 2,588,520 3/52 Halgren 91-420 2,618,121 11/52 Tucker 121-40 XR2,625,177 1/53 Ziskal 121-40 2,653,626 9/53 Fin'layson 121-40 XR2,691,964 10/54 Stickney 91-420 2,716,966 9/55 Hubert et al 121-40 XR2,778,378 1/57 Presnell 137-469 2,872,903 2/59 Richey 121-40 XR2,959,190 11/60 Barnes et a1 121-465 XR 3,015,316 1/62 Thomas 91-4203,126,706 3/ 64 Dettinger 91-420 X WILLIAM F. ODEA, Primary Examiner.

1. A FLOW CONTROL VALVE COMPRISING A BODY HAVING A PAIR OF PASSAGES;VALVE MEMBERS IN THE RESPECTIVE PASSAGES; SPRINGS BIASING SAID VALVEMEMBERS TO POSITIONS CLOSING THE RESPECTIVE PASSAGES; SAID BODY HAVING ACYLINDER THEREIN IN FLUID COMMUNICATION WITH SAID PASSAGES UPSTREAM OFSAID VALVE MEMBERS; A PLUNGER IN SAID CYLINDER HAVING ONE END EXPOSED TOFLUID UNDER PRESSURE IN ONE OF SAID PASSAGES AND THE OTHER END EXPOSEDTO FLUID UNDER PRESSURE IN THE OTHER OF SAID PASSAGES; SAID PLUNGERBEING ADAPTED TO BE MOVED BY PREDOMINANT FLUID PRESSURE IN EITHERPASSAGE INTO ENGAGEMENT WITH THE VALVE MEMBER IN THE OTHER PASSAGE TOMOVE IT TO A POSITION OPENING SAID OTHER PASSAGE; SAID PLUNGER HAVINGFLOW METERING MEANS ON EITHER END THEREOF WHICH ARE OPERATIVESIMULTANEOUSLY TO METER THE FLOW THROUGH BOTH OF SAID PASSAGES WHEN ONEOF SAID PASSAGES IS OPENED BY ENGAGEMENT OF SAID PLUNGER WITH ITSRESPECTIVE VALVE MEMEBER, AND THE OTHER OF SAID PASSAGES IS OPENED BYFLUID PRESSURE EXERTED ON ITS RESPECTIVE VALVE MMBER.